The proliferation of high volume manufactured, portable electronic devices has encouraged innovation in both functional and aesthetic design practices for enclosures that encase such devices. Manufactured devices can include a casing that provides an ergonomic shape and aesthetically pleasing visual appearance desirable to the user of the device. Exterior surfaces of metal alloy casings of portable electronic devices can be shaped by computer numerically controlled machinery and can include combinations of flat regions and curved regions. To minimize weight of the portable electronic device, the metal alloy casing can be shaped to a minimal thickness while maintaining sufficient mechanical rigidity to avoid minor impact damage. As the thickness of the metal alloy casing can be quite thin, for example fractions of a millimeter, the shaping of the exterior casing can require precise and repeatable results to minimize surface variation on the exterior of the casing. Irregularities in the surface can result in a metal alloy casing having an unacceptable appearance or compromised mechanical integrity. In addition, high volume manufacturing can require minimal time for shaping of the metal alloy casing. Multiple separate tools to shape different regions of the metal alloy casing can require additional manufacturing time than machining using a single cutting tool along a single continuous path. Thus there exists a need for a method and an apparatus for machining a three dimensional top surface, edge surface and bottom surface of a metal alloy casing resulting in a surface with a consistent surface variation within a tolerance required to achieve a desired minimal thickness casing and preferred surface appearance upon finishing.